Automation has been requested for a machine tool to further improve the efficiency thereof. The machine tool is provided with a holding device configured to hold an object through a general-purpose clamp mechanism. Automatic replacement of an object held by such a holding device has been requested for further automation of the machine tool.
For example, at a turret lathe (turning center), a tool is held through a tool holder including a built-in general-purpose clamp mechanism. Automatic replacement of a tool attached to such a holder has been requested for further automation of the machine tool.
A large number of general-purpose clamp mechanisms are based on an assumption that the clamp state thereof is manually changed by a worker. For example, in a case of a tool holder including a built-in general-purpose clamp mechanism, a worker inserts a hexagonal wrench into a predetermined hexagonal hole provided to the tool holder and rotates the hexagonal wrench to switch between clamping and unclamping of a tool. However, as described above, it has been desired to automatically change the clamp state of such a clamp mechanism to further improve the efficiency of the machine tool.
In some disclosed technologies, the clamp state of a clamp mechanism is automatically changed, and accordingly, a tool is automatically replaced. For example, in a technology disclosed in JP 2016-144853 A, a tool rotation power source included in a turret is used to change the clamp state of a clamp mechanism of a tool holder coupled with the turret. According to the technology, the clamp state of the clamp mechanism can be automatically changed. However, in the technology of JP 2016-144853 A, it is necessary to use a tool holder (clamp mechanism) having a special structure that allows coupling with a tool rotation motor, and a manually operable general-purpose tool holder cannot be used.
In a technology disclosed in JP 2016-55370 A, a multi-joint arm robot is provided in a fabrication chamber of a machine tool, and a tool is replaced by the multi joint arm robot. The multi joint arm robot includes a plurality of click units each configured to grasp a tool at a leading end, and the tool can be coupled and decoupled by moving the multi-joint arm robot while the tool is grasped by the click units. However, JP 2016-55370 A discloses a technology of moving a tool to couple and decouple the tool, but has no description on how to change the clamp state of a clamp mechanism configured to hold the tool. Thus, the technology of JP 2016-55370 A cannot automatically change the clamp state of a manually operable general-purpose tool holder.
The present specification discloses a machine tool capable of automatically changing the clamp state of a manually operable general-purpose clamp mechanism.